The flexion of the spinal column is done by the abdominal muscles. There are four layers of muscle connecting in the middle of the body/stomach, they are connected to a strong inelastic cord, called the Linea Alba. These four muscles form the rectus sheath.
The muscles of the stomach must be strengthened at all times, so that no untold pressure is placed on the bladder and lower extremities, as well as the lower back. If you are overweight in your stomach area, not only can you feel a constant aching, nagging pain but food cannot be digested with ease, gas and bloating is forthcoming, heartburn will occur, as well as other offensive smells, which will come from the stomach.
The four layers of the stomach are the transversus abdominis, rectus abdominis, internal and external oblique. The transversus abdominis holds the intestine in place, the three other stomach muscles allow for lateral flexion and rotation of the stomach, allowing for side bends and twisting movements.
Great tips to look after your stomach and back when exercising:
Don’t do straight leg sit ups or straight leg lifts together with stomach movements.
Always keep one foot on the ground when doing a stomach exercise, unless you are lifting the hips slightly and are moving up in a ball size position with your knees going toward your navel
Support your head with both hands when doing stomach crunches, but don’t bring your chin onto your chest, curling your neck right in. Don’t clasp fingers behind your head or neck, which forces your chin down, pushing your spine and neck into an unnatural position
Look up ahead, eyes at the ceiling and elbows back, with fingers behind your ears, when you do any type of crunches
Don’t come into a high sit up, swinging your arms and using your arms as a lever to get you up higher, this will automatically push your hips forward and hyperextend your back (over arch) it, and your stomach will not work to it’s maximum capacity, the back will take the strain.